Monitoring cameras that are sensitive to radiation in the infrared range and/or light in the visible range are used to monitor security-relevant areas in passenger aircraft. Such monitoring cameras are used, for example, to monitor cockpit doors, passenger doors, as well as the interior space of passenger aircraft. In complete darkness, as occurs, for example, during night flights, it is also necessary to additionally illuminate the monitoring region during use of monitoring cameras that are sensitive mostly to infrared light. For this purpose, illumination devices are used with light devices that emit radiation in the near-infrared range or in the visible light range. Infrared-emitting diodes or simple light-emitting diodes that emit light in the visible range are widely used as light devices in this context.
In traditional variants of illumination devices for monitoring cameras according to the prior art, a parallel arrangement of the camera optics and the illumination device is common. In order to achieve effective illumination of the monitoring area or the monitoring space in front of the monitoring camera, the infrared-emitting diodes (IRED) or the light-emitting diodes (LED) are arranged either with the camera optics behind a cover panel or the diodes are situated separately arranged on the housing front. The direction of emission of such illumination devices is determined mostly by the emission angle of the diodes as a result of the arrangement of the infrared-emitting diodes or light-emitting diodes parallel to the camera optics.
The already known variants of illumination devices often lead to overexposure of the image center of the image obtained with the monitoring camera, because the main radiation intensity of the diodes points in the direction of the camera optics and therefore to the center of the surveyed object. A higher contrast difference between image information in the image center and the edge regions of the image results from this, so that, for example, automatic evaluation of the image contents by appropriate image processing algorithms for image recognition, for recognition of access authorization and the like is hampered. In addition, security-relevant objects cannot be reliably identified precisely in the edge region of the image, because the image center is overexposed.